For the past 26 years, the Microbiology and Virology Core has supported the projects of this program by creating and maintaining an extensive Infectious Diseases (ID) data base. This data base has been critical for projects that have Infectious Disease endpoints. Over the years the function and services provided by the Core have expanded, mainly driven by the availability of highly sensitive diagnostic capabilities, which made it imperative to have standardized definitions and interpretations of diagnostic test results for the programs. Therefore, all infection endpoints for clinical trials or studies related to the aims of the projects are discussed with the Core director. The Core provides statistical support and data management for specific ID analyses related to the projects. State-ofthe- art diagnostic capabilities are provided and continuous efforts are made to improve diagnostic capabilities for pathogens relevant to hematopoietic stem cell transplant recipients. The Core also maintains a prospective sample and isolate bank. In addition, the Core provides monitoring capabilities for immune reconstitution studies. Specifically, the Core provides the following services: 1. maintaining an electronic ID database, 2. assisting with defining ID endpoints for clinical trials, 3. providing data management for two phase III clinical trials and one observational study, 4. monitoring immune reconstitution in patients undergoing novel transplantation techniques, including immunophenotyping, T cell receptor excision cycles (TREC), and quantitative measurement of pathogen-specific T cell function (e.g., CMV, tetanus) using intracellular cytokine (IFNgamma) and class-I tetramer assays, 5. maintaining a prospective isolate and specimen bank, and 6. development and quality improvement of more sensitive diagnostics for a variety of infections.